Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: fca15e410aef3a78d5f573612079c4692ac54faa
https://github.com/WebKit/WebKit/commit/fca15e410aef3a78d5f573612079c4692ac54faa
Author: Alexey Shvayka <[email protected]>
Date: 2023-06-15 (Thu, 15 Jun 2023)
Changed paths:
M JSTests/ChakraCore/test/LetConst/tdz1.baseline-jsc
M JSTests/stress/const-not-strict-mode.js
M JSTests/stress/lexical-let-not-strict-mode.js
M Source/JavaScriptCore/bytecompiler/NodesCodegen.cpp
Log Message:
-----------
[JSC] delete operator shouldn't perform TDZ checks
https://bugs.webkit.org/show_bug.cgi?id=257697
<rdar://problem/110237888>
Reviewed by Yusuke Suzuki.
ReferenceError for an uninitialized binding is being originated in
GetBindingValue [1], yet delete
operator [2] calls into DeleteBinding instead, which is a no-op [3] in case of
a lexical binding.
This change removes TDZ check and calls into
JSSymbolTableObject::deleteProperty() instead,
which does nothing but returning `false` that is being ignored by del_by_id
opcode in sloppy mode,
precluding a runtime error from being thrown for code like `delete foo; let
foo`.
As for the strict mode, TDZ check isn't even reached because a SyntaxError is
thrown for any binding
that could possibly end up being unitialized [4].
In no way this change affects WithStatement since it can't produce a value
deemed as
uninitialized binding (an empty JSValue).
Aligns JSC with V8 and SpiderMonkey.
[1]:
https://tc39.es/ecma262/#sec-declarative-environment-records-getbindingvalue-n-s
(step 2)
[2]: https://tc39.es/ecma262/#sec-delete-operator-runtime-semantics-evaluation
(step 5.c)
[3]:
https://tc39.es/ecma262/#sec-declarative-environment-records-deletebinding-n
(step 2)
[4]: https://tc39.es/ecma262/#sec-delete-operator-static-semantics-early-errors
* JSTests/ChakraCore/test/LetConst/tdz1.baseline-jsc:
* JSTests/stress/const-not-strict-mode.js:
* JSTests/stress/lexical-let-not-strict-mode.js:
* Source/JavaScriptCore/bytecompiler/NodesCodegen.cpp:
(JSC::DeleteResolveNode::emitBytecode):
Canonical link: https://commits.webkit.org/265212@main
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